摘要:

On the Photochemistry of 1H‐ and 2H‐Indazoles in Acidic SolutionIt is shown that 1H‐ and 2H‐indazoles(cf. Scheme 2)on protonation (0, 1NH2SO4in water or alcoholic solution) give analogous indazolium ions (seeFig. 1and2) which on irradiation undergo heterolytic cleavage of the N (1), N (2) bond whereby aromatic nitrenium ions in the singlet ground state are formed(cf. Scheme 13). If theparaposition of these nitrenium ions is not occupied by a substituent (e.g.a methyl group) they are readily trapped by nucleophiles present (e.g.water, alcohols, chloride ions) to yield the corresponding 5‐substituted 2‐amino‐benzaldehydes or acetophenones(cf. Schemes 4–10). Photolysis of indazole (4) and 3‐methyl‐indazole (5) in 0,75NH2SO4in alcoholic solutions gives in addition minor amounts of the corresponding 3‐substituted 2‐amino‐benzaldehydes and acetophenones, respectively(cf. Schemes 6and8andTable 2). Phenylnitrenium ions carrying a methyl group in theparaposition give in aqueous sulfuric acid mainly the reduction products,i.e.2‐amino‐5‐methyl‐benzaldehydes(cf. Schemes 11and12andTable 3). In methanolic sulfuric acid, in addition to the reduction products, 6‐methoxy substituted benzaldehydes are found(cf. Schemes 11and12andTable 3)which are presumably formed by an addition‐elimination mechanism(cf. Scheme 18). It is assumed that precursors of the reduction products are the corresponding nitrenium ions in the triplet ground state. Singlet‐triplet conversion of the nitrenium ions may become efficient when addition of nucleophiles to the singlet nitrenium ions is reversible(cf. Scheme 22)thus, enhancing the probability of conversion or when conjugation in the singlet nitrenium ions is disturbed by steric effects(cf. Scheme 20)thus, destabilizing the sing

ISSN:0018-019X    

DOI:10.1002/hlca.19790620132

出版商:WILEY‐VCH Verlag GmbH    

年代:1979

数据来源: WILEY

摘要:

On the Photochemistry of 2, 1‐Benzisoxazoles (Anthraniles) and on the Thermal and Photochemical Decomposition of 2‐Azido‐acylbenzenes in Strongly Acidic SolutionAnthranils6(Scheme 3), when irradiated with a mercury high‐pressure lamp, in 96% sulfuric acid yielded, after work‐up, 2‐amino‐5‐hydroxy‐acylbenzenes8and as side products 2‐amino‐3‐hydroxy‐acylbenzenes9(cf. Schemes 5–7andTable 1). When C(5) of the anthranils6carries a methyl group a more complex reaction mixture is found after irradiation in 96% sulfuric acid(cf. Schemes 8and9): 3, 5‐dimethyl‐anthranil (6d) yielded (after irradiation and acetylation) 2‐acetyl‐ amino‐5‐methyl‐acetophenone (15), 2‐acetylamino‐5‐acetoxymethyl‐acetophenone (18d) and 2‐acetylamino‐5‐acetoxy‐6‐methyl‐acetophenone (12c). The latter product was also formed after irradiation of 3, 4‐dimethylanthranil (6c) in 96% sulfuric acid. 3, 5, 7‐Trimethyl‐anthranil (6f) formed under the same conditions 2‐acetylamino‐3, 5‐dimethyl‐acetophenone (15f) and 2‐acetylamino‐5‐acetoxymethyl‐3‐methyl‐acetophenone (18f). Since qualitatively the same product patterns were observed when the corresponding 2‐azido‐acetophenones7were decomposed in 96% sulfuric acid it is concluded that anthranilium ions(cf.6b‐H⊕,Scheme 11)on irradiation are transformed by cleavage of theN,O‐bond into 2‐acyl‐phenylnitrenium ions(cf.25b‐H⊕) in the singlet ground state. The nitrenium ions are trapped directly by nucleophiles (HSO⊖4in 96% sulfuric acid), thus, yielding the hydroxy‐acetophenones8and9(Scheme 11). If C(5) is blocked by a methyl group a [1, 2]‐rearrangement of the methyl group may occur(cf. Scheme 13)or loss of sulfuric acid can lead to quinomethane iminium ions(cf.32‐H⊕,Scheme 13)which will react withHSO⊖4ions to yield, after hydrolysis and acetylation, the 5‐acetoxymethyl substituted acetophenones18dand18f. It is assumed that the reductio

ISSN:0018-019X    

DOI:10.1002/hlca.19790620133

出版商:WILEY‐VCH Verlag GmbH    

年代:1979

数据来源: WILEY

摘要:

Photolysis of 3‐Methyl‐2, 1‐benzisoxazole (3‐Methylanthranil) and 2‐Azido‐acetophenone in the Presence of Sulfuric Acid and Benzene DerivativesIrradiation of 3‐methylanthranil (1) in acetonitrile in the presence of sulfuric acid and benzene, toluene,p‐xylene, mesitylene or anisole with a mercury high‐pressure lamp through a pyrex filter yields beside varying amounts of 2‐amino‐acetophenone (3) and 2‐amino‐5‐hydroxy‐ (4a) and 2‐amino‐3‐hydroxy‐acetophenone (4b) the corresponding diphenylamine derivatives5(seeTable 1). In the case of toluene and anisole mixtures of the correspondingortho‐ andpara‐substituted isomers (5b, 5dor5g, 5irespectively), but nometa‐substituted isomers (5cor5h) are obtained. In addition to these products, the irradiation of1in the presence of anisole yields also 2‐amino‐5‐(4′‐methoxyphenyl)‐acetophenone (7), 2‐amino‐3‐(4′‐methoxyphenyl)‐acetophenone (8) and 2‐methoxy‐9‐methyl‐acridine (6; seeScheme 1). The latter product is also formed thermally by acid catalysis from the diphenylamine derivative5i. Irradiation of 2‐azido‐acetophenone (2) in acetonitrile solution in the presence of sulfuric acid and benzene leads to the formation of1, 3, 4a, 4b, 5aand9(seeTable 2). Compounds3, 4a, 4band5aare also obtained after acid catalyzed decomposition of2in the presence of benzene. Thus, it is concluded that irradiation of1or2in the presence of sulfuric acid yields 2‐acetyl‐phenylnitrenium ions10in the singlet ground state which will undergo electroph

ISSN:0018-019X    

DOI:10.1002/hlca.19790620134

出版商:WILEY‐VCH Verlag GmbH    

年代:1979

数据来源: WILEY

摘要:

On the Photochemistry of 1, 2‐Benzisoxazoles in Strongly Acidic SolutionThe 1, 2‐benzisoxazoles1a, 1band1dwhen dissolved in 96% sulfuric acid and irradiated through a quartz filter with a mercury high‐presure lamp yield, after work‐up, mixtures of 2, 5‐ and 2, 3‐dihydroxy‐acylbenzenes (2and3, respectively;cf. Schemes 1and3andTable 1). Irradiation of 3, 5‐dimethyl‐1, 2‐benzisoxazole (1c) in 96% sulfuric acid leads to the formation of 2, 3‐dihydroxy‐5‐methyl‐acetophenone (3c) in only 6% yield(cf. Table 1). It is assumed that the 1, 2‐benzisoxazolium ions react in the excited singlet state by heterolytic cleavage of theN,O‐bond to yield the corresponding aryl oxenium ions7in the singlet ground state (seeScheme 5). Reaction of7withHSO4⊖ ions, present in 96% sulfuric acid, yields, after hydrolysis, the dihydroxy compounds2and3. Photolysis of 3‐methyl‐1, 2‐benzisoxazole (1b) in diluted sulfuric acid (0,5 to 9M) in methanol or water leads only to the formation of 2‐amino‐phenol (6; seeScheme 3), presumableviaphoto‐isomerization of1bto 2‐methylben

ISSN:0018-019X    

DOI:10.1002/hlca.19790620135

出版商:WILEY‐VCH Verlag GmbH    

年代:1979

数据来源: WILEY

摘要:

AbstractStructural aspects of planoid deformation of tetracoordinate carbon atom, particularly those in annulenes with central carbon atom are discussed. [12] Annulene11with central carbon atom is proposed as compound with strong planoid deformation around the internal carbon centre. The synthesis of a saturated precursor15is described.

ISSN:0018-019X    

DOI:10.1002/hlca.19790620136

出版商:WILEY‐VCH Verlag GmbH    

年代:1979

数据来源: WILEY

摘要:

AbstractLow temperature (−130° to −110°) addition ofexo‐norborn‐5‐en‐2‐ol (7) to excess HSO3F in SO2CIF yielded a mixture ofexo‐5‐(fluorosulfonyloxy)‐exo‐2‐ andendo‐2‐norbornylhydroxonium ions (9+10) under kinetic control that was different from the mixture of9+10obtained by addition ofendo‐norborn‐5‐en‐2‐ol (8) to HSO3F under kinetic control. These mixtures differed from the mixture of9+10observed at higher temperature (−80° to −60°) (thermodynamic control). Addition of 3‐nortricyclanol (23) orexo‐2, 3‐epoxynorbornane (24) to HSO3F at ‐−120° ± 10° yielded a mixture containing theexo‐2‐(fluorosulfonyloxy)‐anti‐7‐ andsyn‐7‐norbornylhydroxonium ions (26+27) as major adducts. Qualitative rates of the isomerization of26+27to the more stable ions9+10and of the isomerization9 ⇄ 10were evaluated. The solvolysis of9+10in HSO3F yielded theexo‐2,exo‐5‐ andexo‐2,endo‐5‐norbornanediyl bis (fluorosulfates) (21+22). Norbornadiene and quadricyclane added 2 equivalents of HSO3F and furnished kinetically a mixture ofexo‐2,anti‐7‐ andexo‐2,syn‐7‐norbornanediyl bis (fluorosulfates) (36+37) as major adducts. The latter36+37were isomerized into a kinetic mixture of the more stable isomers21+22. The rates of these isomerizations were compared. The use of DSO3F and (exo‐2‐D)‐norborn‐5‐en‐2‐ol (15) confirmed that heterolyses of the fluorosulfates were responsible for the observed isomerization; elimination‐addition processes occurred but much more slowly. The results are interpreted in terms of substituted classical and σ‐bridged secondary 2‐norbornyl cation intermediates. It appears that the electron withdrawing substituents FSO3and H2O+(HO) destabilize the σ‐bridged 2‐norbornyl cation more at C(5) than C(7). If the σ‐bridged ions5‐Zsubstituted at C(5) by Z = FSO3or H2O+(HO) are transition states in the isomerization of the corresponding classical ions3‐Z, 4‐Z, the free enthalpy difference between the ‘non‐classical’ σ‐

ISSN:0018-019X    

DOI:10.1002/hlca.19790620137

出版商:WILEY‐VCH Verlag GmbH    

年代:1979

数据来源: WILEY

ISSN:0018-019X    

DOI:10.1002/hlca.19790620138

出版商:WILEY‐VCH Verlag GmbH    

年代:1979

数据来源: WILEY

ISSN:0018-019X    

DOI:10.1002/hlca.19790620101

出版商:WILEY‐VCH Verlag GmbH    

年代:1979

数据来源: WILEY